Indices of insulin sensitivity and secretion from a standard liquid meal test in subjects with type 2 diabetes, impaired or normal fasting glucose

Background: To provide an initial evaluation of insulin sensitivity and secretion indices derived from a standard liquid meal tolerance test protocol in subjects with normal (NFG), impaired fasting glucose (IFG) or type 2 diabetes mellitus. Methods: Areas under the curve (AUC) for glucose, insulin and C-peptide from pre-meal to 120 min after consumption of a liquid meal were calculated, as were homeostasis model assessments of insulin resistance (HOMA2-IR) and the Matsuda index of insulin sensitivity. Results: Subjects with NFG (n = 19), IFG (n = 19), and diabetes (n = 35) had mean +/- SEM HOMA2-IR values of 1.0 +/- 0.1, 1.6 +/- 0.2 and 2.5 +/- 0.3 and Matsuda insulin sensitivity index values of 15.6 +/- 2.0, 8.8 +/- 1.2 and 6.0 +/- 0.6, respectively. The log-transformed values for these variables were highly correlated overall and within each fasting glucose category (r = -0.91 to -0.94, all p < 0.001). Values for the product of the insulin/glucose AUC ratio and the Matsuda index, an indicator of the ability of the pancreas to match insulin secretion to the degree of insulin resistance, were 995.6 +/- 80.7 (NFG), 684.0 +/- 57.3 (IFG) and 188.3 +/- 16.1 (diabetes) and discriminated significantly between fasting glucose categories (p < 0.001 for each comparison). Conclusion: These results provide initial evidence to support the usefulness of a standard liquid meal tolerance test for evaluation of insulin secretion and sensitivity in clinical and population studies.